The development of a new method for the synthesis of 1,1-dioxido-1,2-benzisothiazoline-3-acetic acid by a domino process is reported whereby a classical Heck reaction is coupled to an intramolecular aza-Michael reaction. Ultimately, this method has been expanded to a one-pot, sequential three-component protocol to generate diverse benzofused γ-sultams from a range of commercially available α-bromobenzenesulfonyl chlorides, amines and Michael acceptors.